The present invention relates to a rotary damper used in a vehicle such as an automobile.
In a vehicle such as an automobile there are provided various receptacle portions within a passenger compartment. Some such receptacle portions are provided with a lid that closes when it is pushed once and opens when it is pushed once more. One such lid, which is supported through a rotary damper, is disclosed in Japanese Patent No. 2544628.
As shown in FIGS. 7 and 8, this rotary damper includes: (a) a cylindrical rotor 1 that receives a rotational input, (b) a housing 2 that has a shaft 3 that is fitted in an inner periphery of the cylindrical rotor 1 and also has a cylindrical wall 4 that surrounds the shaft 3. A viscous fluid 5 is interposed between the inner periphery of the cylindrical rotor 1 and the shaft 3 of the housing 2. A coiled spring 6 is interposed between an inner periphery of the cylindrical wall 4 of the housing 2 and an outer periphery of the cylindrical rotor 1. The coiled spring 6, which is fixed at one end thereof to the housing 2 and at an opposite end thereof to the cylindrical rotor 1, is tightened with rotation of the cylindrical rotor 1, which rotation is performed upon receipt of a rotational input in the cylindrical rotor. A cover 7 is fixed to the housing 2 so as to close an open end face of the cylindrical wall 4 of the housing; an inner surface of the cover 7 is opposed to an end face of the cylindrical rotor 1. A spiral groove 9, which is formed in one of the inner surface of the cover 7 and the end face of the cylindrical rotor 1, is provided at one end thereof with a heart cam groove 10. An operating pin 8 is mounted to the other of the cover 7 and the cylindrical rotor 1 and is guided through the spiral groove 9.
An input/output shaft 12, which projects outward from the cover 7, is integral with the cylindrical rotor 1; a lid of a receptacle portion is attached to the input/output shaft 12.
The heart cam groove 10 is provided with: (a) heart island 10′, (b) end portions 10a and 10c of two arcuate and straight paths, respectively, that are formed along both side portions of the heart island 10′, and (c) a slit 10b that is formed in a rear end portion of the heart island 10′ at an intermediate position of a path that interconnects the arcuate and straight paths at positions near the two end portions 10a and 10c. 
When the lid is pushed into a closed state from an open state, the input/output shaft 12 connected to the lid is rotated. Thus, when the lid is pushed, a rotational force is imparted to the cylindrical rotor 1 through the input/output shaft 12. As a result of the rotational force, the coiled spring 6 is tightened and a restoring force is accumulated in the spring. At this time, the operating pin 8 moves along the spiral groove 9 to a first end side from an opposite, second end 9′ side of the same groove, i.e., toward the heart cam groove 10 that is formed at the first end side of the spiral, groove 9. The pin then reaches one end portion 10a of the heart cam groove 10 through the arcuate path of the same arcuate groove. Subsequently, the pin 8 returns slightly and is caught (i.e., stopped) in the slit 10b of the heart island 10′, thereby maintaining the lid in a closed position.
When the lid is pushed again, the operating pin 8 is disengaged from the slit 10b formed in the heart island 10′. The pin 8 then moves to the other end portion 10c of the heart cam groove 10. Subsequently, with the restoring force of the coiled spring 6, the pin 8 linearly returns from the other end portion 10c of the heart cam groove 10 to the first side of the spiral groove 9. Thereafter, the pin 8 moves to the opposite, second end 9′ side of the spiral groove 9, at which the lid opens.
In such a conventional rotary damper, however, as the operating pin 8 is provided on the cover 7 side of the cylindrical rotor 1, a vertical size of the entire device becomes large, i.e., the device is not of a compact size. Moreover, as the device uses the cylindrical rotor 1, the housing 2, and and the cover 7, the number of components, and hence the cost, is high.